In recent years, along with the developments in science and technology, there has been a strong demand for minute structural members in various fields, and related research has been vigorously conducted with respect to devices such as micro-actuators, electronic devices and optical devices. For example, various small-size sensors, microprobes, thin-film magnetic heads, ink jet heads and the like have been put into practical use. With respect to the method for manufacturing such a minute structural member, various methods, such as a stamper, dry etching and photolithography, have been used. Among these methods, pattern formation though photolithography using a photosensitive resin material has advantages in that a desired shape with a high aspect ratio is easily obtained with a high level of precision. The resist to be used for photolithography is mainly classified as a negative type resist or a positive type resist. In particular, when such a structural member that is used as a part on a substrate is formed, the negative type resist is mainly desirable for use. Moreover, from a viewpoint of the purpose of use, when the minute structural member requires anti-chemical properties and when the minute structural member needs to be used with a comparatively thick film thickness in a range from several microns to several tens of microns, a cationic polymerizable resin material using an epoxy resin, a vinyl ether compound or the like as its base is generally used.
In general, when a minute structural member is formed by using an epoxy-based photosensitive resin material, a cationic polymerizable epoxy resin or an epoxy oligomer, or cationic photopolymerizable epoxy resin composition made from a cationic photopolymerization initiator, such as a photoacid generator, is used. In such a cationic photopolymerizable epoxy resin composition, an acid is generated by exposure, and the ring-opening polymerization of the epoxy group advances by using the acid as a catalyst through a heating process after exposure (PEB). In this case, the patterning property tends to be adversely effected by various environmental factors such as diffusion of the acid to an unexposed portion, basic components in the air and the state of the face with which the resin is made in contact. For this reason, in an attempt to form a further minute pattern, degradation in the resolution and size-controlling property tends to occur.
For example, with respect to a negative type resist of a chemical amplifying type, in order to solve problems similar to the problem described above, a method in which, for example, a substance having a function for deactivating acid is preliminarily contained in resist has been proposed in order to prevent the acid generated in the exposed portion from diffusing beyond the necessary degree (Japanese Patent Application Laid-Open No. H05-127369, Japanese Patent Application Laid-Open No. H05-232706, Japanese Patent Application Laid-Open No. H09-325496).
In the field of ink jet heads, in general, the head is always made in contact with ink (that is, in general, ink that is mainly composed of water, and is not neutral) during its use. Therefore, in the case of a head with a large recording width, there have been strong demands for a material with a low water absorption, which is superior in anti-ink properties, mechanical properties and adhesion to the substrate, as the constituent member for the ink jet head. In order to solve the above-mentioned problems, in Japanese Patent Application Laid-Open No. H08-290572, the applicant of the present invention has disclosed a method for manufacturing an ink jet head in which the constituent member of the ink jet head is formed by a cured matter of a resin composition that contains a curable epoxy compound, a compound containing fluorocarbon and a curing agent, with the content of the compound containing fluorocarbon being set in a range of 1 to 50 wt %. In the above-mentioned Patent Gazette, an ink supply port is formed through dry etching in which oxygen plasma is used.
In order to further improve the patterning property and also to improve the properties such as anti-ink properties and adhesion to the substrate, the inventors of the present invention carried out a pattern forming process in which a substance having a function for deactivating an acid and a fluorocarbon are contained in a cationic photopolymerizable epoxy resin having a cationic polymerizable epoxy resin and a cationic photopolymerization initiator. As a result, it was found that desired properties are not obtained, and that crater-shaped holes are observed on an interface (exposure interface) between the unexposed portion and the exposed portion in the depth direction, with the result that, to the contrary, the patterning property further deteriorates.